A dye-sensitized solar cell is advantageous because it is manufactured at a cost lower than when manufacturing a conventional silicon solar cell and exhibits high energy conversion efficiency in comparison to the cost. Further, the dye-sensitized solar cell may be provided in the form of a transparent and flexible cell, thus enabling the application thereof in various fields. The dye-sensitized solar cell is composed of a photoelectrode including dye molecules for absorbing light in a visible range to produce electron-hole pairs and titanium dioxide (TiO2) transition metal oxide for transferring the produced electrons, and a counter electrode including a platinum layer functioning as a catalyst of a redox reaction of an electrolyte solution. The photoelectrode which is present in the form of a porous film is formed of an n-type oxide semiconductor having a wide band gap such as titanium dioxide (TiO2), zinc oxide (ZnO) or tin oxide (SnO2), the surface thereof being adsorbed with a dye in a monomolecular layer form. When sunlight is radiated onto the solar cell, electrons near the Fermi energy in the dye absorb the solar energy and are excited to an upper level that is not occupied with electrons. Further, the vacant lower level resulting from escape of the electrons is occupied again with electrons supplied by ions in the electrolyte. The ions that supply electrons to the dye move to the photoelectrode, so that they receive electrons. During this procedure, the platinum counter electrode acts as a catalyst for a redox reaction of the ions in the electrolyte solution, thus supplying electrons to the ions in the electrolyte via the redox reaction on the surface thereof.
In order to improve the energy conversion efficiency of the conventional dye-sensitized solar cell, Korean Unexamined Patent Publication No. 2003-0032538 discloses a method of increasing photocurrent, in which a mixture layer of titanium dioxide (TiO2) and titanium silicalite-2 is formed to increase scattering of light so as to improve the ability of a dye to absorb light. In the manufacture of the conventional photoelectrode, the dye-sensitized solar cell resulting from the use of the mixture of titanium silicalite-2 is problematic in that the energy conversion efficiency for converting sunlight into electrical energy is still low. Therefore, many attempts to increase the efficiency of the solar cell are made.